This invention relates generally to sheet feeders for automatic collating equipment. More particularly, the invention relates to an improved sheet feeder apparatus which significantly increases throughput by the multiple sequential feeding of sheets, whereby more than one sequence is carried out simultaneously.
In today's fast paced information industry there is a growing need for automatic sheet feeding equipment. Automatic sheet feeders are found in many printing machines, typesetting machines, laser printers and photocopying machines already, and use is expanding. With the recent advances in printing and photocopying technology, it is proving to be increasingly difficult to build sorting and collating equipment which can keep up with the printing or copying process. High volume printing and photocopying operations now rely heavily upon automatic sheet feaders for sorting and collating sequentially arranged sheets into books, reports, manuals, and other lengthy documents. Already the rate at which sheet feeders operate has proven to be a significant limiting factor in the speed at which collated works can be printed, copied and assembled. Accordingly, there is a continuing need to improve such sheet feeding equipment.
Traditionally, sheet feeders have operated by sequentially selecting ordered sheets or pages from sequentially arranged bins. To assemble a completed document the sheet feeder would first eject the starting page from bin 1, next the second page from bin 2, and so forth until the final page was ejected. Such a sheet feeder operated in a sequential fashion, completing one collated work before starting the next.
In an effort to improve throughput, later sheet feeders were developed which ejected all pages for one complete work simultaneously from their respective bins. The pages then traveled along respective paths of varying length, so that the first page of the work would arrive at the assembly station prior to the second page, the second page would arrive prior to the third page, and so forth. While the simultaneous feeding mechanism did improve throughput, these mechanisms were plaqued with other problems. For example, if through malfunction, a given page did not eject, then the remaining pages would nevertheless arrive at the assembly station without the missing page. Although such condition could be detected, it was not easy to insert the missing page at the proper place in the incomplete work. Thus, the incomplete work would often have to be removed from the assembly apparatus and either re-sorted back into the original feeder bins or discarded.
It is an object of the present invention to overcome the foregoing deficiencies in prior art sheet feeding mechanisms. It is a further object of the invention to provide a sheet feeding apparatus which greatly improves sheet feeding throughput without the problems encountered in the prior art. It is yet another object of the invention to provide a sheet feeding apparatus which increases throughput by sequentially feeding sheets in overlapping cycles whereby a first batch of pages is fed for assembly into a first completed document before the preceding batch of pages comprising a preceding document has been completed. It is a further object to provide a sheet feeder apparatus which may be incorporated into existing equipment to improve feeding throughput.
The invention thus provides a sheet feeder which comprises a plurality of bins for holding sheets to be fed and a sheet extracting apparatus. The sheet extracting apparatus comprises a plurality of extraction means, one of the plurality of extraction means being associated with each one of the bins, for extracting at least one sheet therefrom upon actuation. The invention further comprises a control means for establishing a sheet feed cycle and for causing the extraction of the sheets from the bins during the sheet feed cycle. The control means includes a timing means for producing a predetermined sequence of timing signals during each sheet feed cycle. A switching means is responsive to the timing means and selectively actuates selected ones of the extraction means. The timing means is configured to provide overlapping sheet feed cycles, wherein the last sheet of a first occurring sheet feed cycle is extracted from its bin after the first sheet of a second occurring sheet feed cycle is extracted.
For a more complete understanding of the invention, its objects and advantages, reference may be had to the following specification and to the accompanying drawings.